Anti-Aliasing (AA) is a computer graphics technique that attempts to minimise the unwanted 'staircase' or jagged object outlines which occur due to the limited resolution in 3D-Renderers, essentially by 'smoothing' these lines.[1]

Also known as Full Scene Anti-Aliasing (FSAA) and often interchangeable with the term downscaling.

Technically when implemented correctly, these do differ in that downscaling applies to an entire frame buffer – 2D and 3D Elements, while SSAA/MSAA are techniques only applied internally to 3D elements. In some implementations this can result in a lesser performance impact and better compatibility.

Applies the general anti-aliasing formula to full screen images, reducing the "staircase effect". When compared to a rendered image undergoing MSAA, a SSAA/FSAA image will appear smoother. 2D text can also be affected by most downscaling implementations, while SSAA/MSAA should not affect text when implemented correctly.

Has largely been replaced by less resource intense methods due to the huge stress it puts on the GPU, but due to the better result that it provides, some games still adopt it as an option in the in-game settings.[3]

To reduce the stress that SSAA/FSAA puts on a system, multi-sampling optimizes the process by evaluating each pixel only once, with true super-sampling only occurring at the edges of a rendered object, and to depth values. This results in a similar (but less drastic) improvement in visual quality whilst reducing the load put on the system to render and downscale such high resolutions.[4]

Primarily clears up aliasing on geometry; temporal aliasing and aliasing from shader effects, textures and transparencies will not be affected.[5]

Maxwell based GPUs such as GTX 750 Ti and GTX 800M/900 series removed the support[7]

Aims to further reduce the additional stress that MSAA puts on the system, with Nvidia claiming that a CSAA-rendered image will rival 8x-16x MSAA whilst only putting a load on the system comparable to 4x MSAA. It does this by reducing the number of settings each sample determines (by creating a new sample for coverage) whilst increasing the overall number of samples.

AMD claims it offers enhanced AA quality over standard Multi-Sample Anti-Aliasing modes by adding more coverage samples per pixel but keeping the same number of color/depth/stencil samples to achieve better AA quality than standard MSAA modes.[9]

Transparency version is enabled simply by setting it in Nvidia control panel. Full Scene requires one to set Antialiasing - Mode to Override any application settings, Antialiasing - Setting to either 2x 4x or 8x multisapling and Antialiasing - Transparency to the same value you set Antialiasing - Setting.[11] Note that your game may need a particular compatibility string, see here for more info; Nvidia Profile Inspector is needed.

Applies anti-aliasing not only to the current frame but also to some frames that were rendered before, restoring the old positions of pixels by using their velocity. This creates smoother and more cinematic images in the game, while only slightly increasing the load on your video card.[16]

Does not require large amounts of computing power. It achieves this by smoothing jagged edges ("jaggies")[21] according to how they appear on screen as pixels, rather than analyzing the 3D models itself as in conventional anti-aliasing

However, the image quality improvement it provides is significantly less impressive than traditional AA methods such as MSAA.[22]

CMAA is positioned between FXAA and SMAA 1x in computation cost (1.0-1.2x the cost of default FXAA 3.8 and 0.55-0.75x the cost of SMAA 1x)

Compared to FXAA, CMAA provides significantly better image quality and temporal stability as it correctly handles edge lines up to 64 pixels long and is based on an algorithm that only handles symmetrical discontinuities in order to avoid unwanted blurring.[26]

References

"One more rather important disadvantage is that, due to separating the lighting stage from the geometric stage, hardware anti-aliasing does not produce correct results anymore since interpolated subsamples would result in nonsensical position, normal, and tangent attributes."